Hydrophobizing agents are widely used as water repellent materials to impart water resistance to such compositions as textiles, carpet fibers, and paper and paperboard, when applied thereon. Hydrophobizing agents can be also used to prevent corrosion of metal surfaces, when used either alone, or in combination with other materials, as components of corrosion inhibiting coatings. Many materials are known in the art to be useful as hydrophobizing agents including organometallic complexes, such as organo-soluble divalent or trivalent metal ion salts of sulfonate group-containing compounds, waxes and wax-metal emulsions, resin-based finishes, silicones, rosin, hexadecylketene dimers, and fluoro chemicals. A general review of the many types of water repellent chemicals useful as hydrophobizing agents is provided by M. Hayek in the Encyclopedia of Chemical Technology, Volume 24, (1984), "Waterproofing and Water/Oil Repellency" pages 442 through 465, and is incorporated herein by reference.
It is well known in the art that many hydrophobizing agents can be stabilized in aqueous dispersion form by the presence of surfactants, usually fatty acid salts, or salts of sulfated fatty alcohols, in order to facilitate their handling and application onto materials, especially at surfaces or at interfaces, for the purpose of imparting water repellency. Such dispersions typically contain relatively high concentrations of surfactant and/or protective colloids as dispersion stabilizers, typically greater than 10% by weight based on hydrophobizing agent, the presence of which surfactants or protective colloid dispersion stabilizers, while providing the necessary colloidal stability for practical preparation of such aqueous dispersions, and while providing the necessary surface activity to ensure deposition of the hydrophobizing agent at surfaces or interfaces, detracts from the repellency properties desired upon final application. This results from the presence of the hygroscopic surfactant or protective colloid dispersion stabilizer in the resulting water repellent layer, which promotes aqueous rewetting and swelling of the deposited hydrophobizing agent.
It is known that hydrophobizing agents comprising organo-soluble multivalent ion salts of sulfonate group-containing compounds, for example organo-soluble divalent or trivalent metal ion salts of sulfonate group-containing compounds, are particularly suited as corrosion inhibitors, providing corrosion protection in commercial rust preventative formulations for ballast tank coatings, temporary parts protectorants, corrosion-resistant greases, seam sealants, penetrants, adhesives, and numerous automotive and small parts coatings. For example, materials such as overbased calcium sulfonates derived from petroleum sulfonates are widely used in coatings, as they provide high resistance to chloride induced corrosion, good coating rheology, good surface wetting characteristics, water resistance or water repellency, and broad compatibility when blended with many hydrocarbon oils, petrolatums, and resins. Typically, these materials are applied as 100% solids or as solutions in organic oil carriers, which can lead to difficult handling and clean up procedures, and safety issues associated with the flammability of the solvents.
While water-borne dispersions containing overbased calcium sulfonates are known, and would be expected to overcome many of the issues just described, stabilization of the aqueous dispersion typically requires high levels of surfactants in order to achieve sufficient stability to enable the aqueous dispersion to be transported and handled prior to application. For example, U.S. Pat. No. 5,660,890 describes a water-based soft coating for metals wherein a water compatible overbased alkaline earth alkyl-aryl sulfonate is used as a rust inhibitive component. This material is provided as an emulsifiable rust-inhibitive concentrate, containing a surfactant formulated therein. It is known that high surfactant concentrations detract from the water repellency of the final coating; at least partially negating the benefit of the application of the corrosion protectorant in the first place. Thus it would be advantageous to provide aqueous dispersions of hydrophobizing agents comprising organo-soluble multivalent ion salts of sulfonate group-containing compounds, such as organo-soluble divalent or trivalent metal ion salts of sulfonate group-containing compounds, which contain low levels of surfactants or which contain no surfactant at all, in order to improve water repellency or water resistance, without sacrifice to the ability of the dispersion to impart corrosion inhibiting properties to surfaces.
Several examples of solvent-borne coatings for metal surfaces are provided. U.S. Pat. No. 4,157,991 discloses coating compositions for protecting metal surfaces having controlled proportions of an alkyl ammonium alkyl phosphate and a high molecular weight petroleum sulfonate to inhibit corrosion, silicone and silicone alkyd resins to provide a physical barrier, i.e. water repellency, trichlorotrifluoroethane and an aromatic hydrocarbon as solvents, and isopropyl alcohol as a coupling agent. An organo-soluble, water-insoluble ethyl cellulose thickener is utilized to control viscosity and vertical run-off of the coating. No mention is made of water-borne coatings or water-borne versions of such organo-soluble coatings. A similar solvent-borne strategy is disclosed in U.S. Pat. No. 4,294,619, wherein an organo-soluble, ethyl hydroxy ethyl cellulose thickener is utilized to control viscosity and vertical run-off of the coating. In this case, an organic solvent solution of ethyl hydroxy ethyl cellulose thickener and dispersed pigment is prepared, to be mixed with a partially hydrolyzed ethyl silicate resin as part of a two-component coating system. Furthermore, U.S. Pat. No. 5,338,346 relates to a soft coating for ferrous metal surface tanks, having a thickness of about 1-10 mils, comprising overbased alkaline aliphatic-aromatic organic sulfonate salt, an alkaline earth metal or zinc salt of a naphthalene sulfonate, a drying oil, a metal drier, and a paraffinic oil. The coating is particularly useful for coating ferrous metal surfaces, such as ballast tanks, which are exposed to sea water. No mention is made of water-borne coatings or water-borne versions of such organo-soluble coatings.
It is not surprising that water-borne coatings are not mentioned in the solvent-borne coatings patents described above since it is well known that the presence of water during the coating process can initiate the corrosion process itself. Nevertheless, to simplify safe handling and clean up procedures, it would be advantageous to have water-borne coatings which provide the corrosion inhibition and water repellency of the corresponding solvent-borne coatings.
Rust removing aqueous compositions or water-soluble temporary liquid spray masks are also known. Thus EP 256728 A2 880224 describes rust converting aqueous wash compositions, optionally containing water-soluble thickeners, for removing pre-existing rust, while U.S. Pat. No. 5,201,946 discloses a water-soluble liquid temporary masking composition to be spray-applied in film form to a limited area of a configured surface having a contiguous area to be coated for suppressing dust and marring in the limited area. In neither instance are advantages of corrosion prevention and water repellency combined in the form of a water-borne coating.
It is also taught in the art that water-soluble hydrophobically modified water-soluble cellulose ethers are useful in thickening and stabilizing aqueous emulsions, dispersions, and suspensions. For instance, U.S. Pat. Nos. 4,352,916 and 4,868,238 disclose that use of water-soluble hydrophobically modified nonionic cellulose ethers and carboxymethyl hydrophobically modified hydroxyethyl cellulose, respectively, provide improved particle size and less latex formation in suspension polymerization processes. In addition, U.S. Pat. Nos. 4,684,704, 4,845,175 and Eur. Pat. Appl. EP 489425 A1 920610 disclose aqueous dispersions having improved properties prepared by emulsion polymerization in the presence of water-soluble hydrophobically modified hydroxyethyl cellulose. Furthermore, U.S. Pat. No. 4,784,693 describes cementing compositions and aqueous hydraulic cementing solution comprising water-soluble, nonionic hydrophobically modified hydroxyethyl cellulose. Water-soluble polymeric surfactants derived from hydroxyethyl cellulose useful in emulsion stabilization/flocculation are described in Czechoslovakia Patent CS 214392 B 840601, Journal of Applied Polymer Science 40(3-4), 333 (1990), and Faraday Discuss. Chem Soc. 90, 323 and 365 (1991). Still further, emulsion compositions containing water-soluble alkylhydroxyalkyl cellulose derivatives for imparting artificial tan to human skin is disclosed in WO 9316683 A1 930902. Finally, several publications describe the use of water-soluble alkylhydroxyalkyl celluloses as thickeners for architectural coatings, including Eur. Pat. Appl. EP 562341 A1 930929, and Prog. Org. Coat. 22(1-4), 245 (1993). None of these disclose the use of water-soluble hydrophobically modified water-soluble cellulose ethers as stabilizers or emulsifiers for the production of aqueous dispersions of hydrophobizing agents comprising organo-soluble multivalent ion salts of sulfonate group-containing compounds such as organo-soluble divalent or trivalent metal ion salts of sulfonate group-containing compounds.